1. Field of the Invention
The present invention relates generally to flat panel display technologies and, more particularly, to thin display devices including, but not limited to, liquid crystal display (LCD) panels with a built-in backlight module.
2. Description of the Related Art
In display apparatus of the type using a liquid crystal (LC) panel representative of thin-type displays, an illuminating device is traditionally designed to use a cold cathode tube as the light source of a backlight module. In recent years, large screen size LCD television (TV) receivers using semiconductor light-emitting diode (LED) elements as the light source of its backlight are developed and commercially announced in the marketplace. Additionally, a light source of the backlight for use in small screen size LC panels for mobile cellular phones is typically designed to employ a white light source which is made up, in combination, of more than one blue-color semiconductor LED and yellow-color fluorescent material.
In the semiconductor LED elements (simply referred to also as “LEDs” hereinafter) used for these applications, these are conventionally arranged to be of the area light emission type capable of enlarging spread angles of outgoing light. An example of the LED-using illumination device is disclosed, for example, in S. Nakamura et al., Jpn. Journal of Appl. Phys., 34, L1332 (1995), wherein both electrodes for the power feed use are disposed on a one-side surface of the LED element to thereby attain the current-flowable area emission type for permitting the entire element to emit light, which is then taken out from the side of an optically transparent substrate.
In addition, an approach to improving the device characteristics of LEDs is disclosed in JP-A-2001-144326 and JP-A-2004-96132, wherein a technique for increasing the intensity of outgoing polarized light components as emitted from a light emission layer is used to enhance the efficiency of take-out of the emitted light to thereby increase the external quantum efficiency. Moreover, in order to make active use of polarized light components with respect to an LC panel, JP-A-8-306954 and JP-A-9-302107 involve therein the teachings as to a scheme for manufacturing an uniaxially oriented polymer which enhances the polarized light of a polymer organic light emissive device. Additionally, an illumination device of LC panel which uses in combination LEDs and a polarization plate(s) to guide illumination light to fall onto a light guide plate is known, examples of which are disclosed in JP-A-2002-365634 and JP-A-2003-7114.